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mold/test/elf/gnu-unique.sh
Rui Ueyama e65c5d2a1c [ELF] Handle ABI incompatibility between -fgnu-unique and -fno-gnu-unique
GCC creates symbols in comdat groups as STB_GNU_UNIQUE instead of STB_WEAK
if it was configured to do so at build time or the -fgnu-unique option was
given. If mold is given two object files with and without STB_GNU_UNIQUE,
it could end up selecting a sybmol that is in a de-duplicated comdat group.

This is arguably just an ABI incompatibility. Two comdat groups must
contain the same contents if their identifiers are the same. But we
can't handle it as an error because it is not uncommon to link object
files compiled using Clang (or GCC without -fgnu-unique) to static
libraries built with GCC that produces STB_GNU_UNIQUE symbols.

This patch gives the same priority to STB_GNU_UNIQUE as STB_WEAK so that
mold won't select symbols in discarded comdat groups.

Frankly, the situation around STB_GNU_UNIQUE is a mess. That GNU extension
shouldn't have been added to the GNU toolchain in the first place.
It looks like GCC shipped with Linux distros are nowadays do not produce
STB_GNU_UNIQUE symbols by default, but we still need to handle them.

Fixes https://github.com/rui314/mold/issues/324
2022-02-07 07:53:58 +09:00

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Executable File

#!/bin/bash
export LANG=
set -e
CC="${CC:-cc}"
CXX="${CXX:-c++}"
testname=$(basename "$0" .sh)
echo -n "Testing $testname ... "
cd "$(dirname "$0")"/../..
mold="$(pwd)/mold"
t=out/test/elf/$testname
mkdir -p $t
which g++ >& /dev/null || { echo skipped; exit; }
cat <<EOF | g++ -o $t/a.o -c -std=c++17 -fno-gnu-unique -xc++ -
inline int foo = 5;
int bar() { return foo; }
EOF
cat <<EOF | g++ -o $t/b.o -c -std=c++17 -fgnu-unique -xc++ -
#include <stdio.h>
inline int foo = 5;
int main() {
printf("foo=%d\n", foo);
}
EOF
$CC -B. -o $t/exe $t/a.o $t/b.o
$t/exe | grep -q 'foo=5'
echo OK